Protective means for railway vehicle motors



4 Sheets-Sheet 1' PROTECTIVE MEANS FOR RAILWAY VEHICLE MOTORS Sept. 29,

INVENTOR Char/e5 G h/hl/fafief.

'ATTORNEY Sept. 29, 1931. c, c, wHlTTAKER 1,824.855

PROTECTIVE MEANS FOR RAILWAY VEHICLE MOTORS Filed May 17, 1928 4Sheets-Shet 2 85 ATTORNEY Sept. 29, 1931. c, 1, wHn ER 1,824,855

PROTECTIVE MEANS FOR RAILWAY VEHICLE MOTORS Filed May 1'7, 1928 4Sheets-Sheet 3 fig? 7.

75/1401?) Reservoir.

INVENTOR Char/es'ivhfifaker:

A'i'TORNEY 75114915 Eeservo/k' Sept. 29, 1931. c. WHITTAKER- 1,824,855

PROTECTIVE MEANS FOR RAILWAYVEHICLE MOTORS Filed May 17. 1928 4Sheets-Sheet 4 B Fig/L E79: /2.

a bcdefghz iz INVENTOR Charles G W/w'ffa/ien 83w BY .w I gm PatentedSept. 29, 1931 UNETE.

CHARLES C. WHIrrAKEaor PITTSBURGH, rnnnsvnvnnxa sssmnon roiwnszriiimHOUSE ELECTRIC 8c MANUFACTURING VANIA Application filed May 17,

My invention-relates generally to railway vehicles and particularly toprotective means for the traction apparatus provided for propellingrailwayvehicles.

Railway vehicles, such as locomotivesprovided with direct-currentmotorsor singlephase commutating motors, may be damaged during the startingperiod-by applying a heavy current to the starting motors, if the Atrain to which. the locomotive is attached does not start immediately.

In starting trains requiring t-wo or-more.

locomotives, power may be applied to one locomotive and it may'exert itsfull tractive eiiort before current is apphed to the motors ot' theother locomotives, and, under such conditions, the entire, startingcurrent will pass through a limited number of commu tator bars and coilsin'ea'ch of the driving motors of the first energized locomotive untilthe other locomotives take up their share of the load. i

The object of the invention, generally stated, is to provide forlimiting the time during which current may flow'continuously through anygroup of commutator bars to prevent excessive heating.

Another ObJQCiZ oi the invention is to provide for causing relatlvemovement between i the brushes and commutator cylinder ofa propellingmotor of an electrical locomotive, during the process of starting atrain, to prevent excessive heatingot any of the commutator bars. i v Afurther object of the invention is to ac complish relativemotion'between the commutator cylinder and'the brushes of the drivingmotor of a locomotive by providing means for oscillating the locomotiverelative to the train to which it maybe attached.

Anotherobject of the invention is to proide a draw-bar mechanism that isdisposed to be oscillated in alongitudinal direction relative to thelocomotive, whereby the locomotive may he moved relative to the train towhich it is attached, y c It will be apparent, upon studying thefollowing dcscription, that these and other objects of the inventionmaybe attained by means of theapparatus shown in connection COMPANY, A

JCOBPOBATIOYN or PENNSYD PROTECTIVE MEANS FOR RAILWAY vEnicLn' Morons1928. Serial N6. 273,465.

panying drawings; in which,

with an electrical locomotive inthe "accom-' Figure l'is' a view, inside elevation, ofone end of a locomotive equipped with anoscillatingdraw-bar mechanism that embodies the invention; Fig. 2 is a planview,partially in section, ofthe oscillating draw-bar mechanismem bodiedinthe locomotive" shown inFigi 1 i Fig. 3 is a view,'in side elevation, ofthe draw-bar nieclianisiirshowlrin Fig. 2;

Fig. 4 is a plan view, partially in section, oi -a modified far ofdraw-bar mechanism taken along the line I V IV of 5;

Fig; 5 is a view, in side elevatiomjof the modified Qdraw-bar mechanismshown in 5 1 1 i I ii Fig. 6'is'a view, inlongitudinal section,ofanother modification ofthe invention \Fig. 7- 's a schematic diagram"of the'hydraulic system used in connection 'Withthe draw-bar mechanismshown i n'F igs.'-1to 5;

Fig. 8 is a schemati'cdiagram-of a hydraulic oscillating system that isdisposed-to operate the draw-bar mechanisms at either end of alocomotive simultaneously;

Fig. 9is a view, inside elevation, of an electrical locomotive equippedwith oscillating devices embodying the invention and positioned withina'-train;'

Fig. l0 is'ja plan'view, in cross-section, of a valve :mechanismutilized in connection with the hydraulic system; 7

F ig, 11 is aview, in cross section, sofa portion of the valvemechanism, taken along the line XIXI of Fig lO; and,

Fig. 12 is a diagramofthe-locomotive control drum and the electricalcircuitutilizedfor controlling. the oscillating mechanism i i Referringto thedrawings, Fig. 1 showsa bar and coupling mechanism 8.that isdisposed to connect the locomotive to. a trainof r cars (not shown) thatmay be represented by a draw-bar and coupling device 9.

To provide means for driving the locomotive, the driving axle 3 hasattachedto it a gear wheel 12 that meshes with a pinion 13 mounted on adriving motor 14. The driving motor 14; is suspended from the framemember 2 by means of a spring suspension link 15 and is provided withthe usual commutator cylinder 16 and cooperating brushes 17. The framemember 2 further serves to support a cab or body portion 21 thatencloses the driving motor '14 and other. electrical equipment, as well,as provides accommodations for the locomotive operator.

Under certa n starting conditions, the electrical locomotive 1 may exertits full starting traotive effort for some time before thetr'ain, whichis represented in Fig. 1 by the draw-bar 9, starts to move. It will beevident that, if some-means is provided for moving the commutator.cylinder 16 relative to the brushes 17, during the starting period in,such manner that the'current is caused to flow through successive coilsprogressive- 1y,- fdanger off'excessivelyheating portions of the motorrotor will'*be avoided. In the locomotive shown in Fig.1, the desiredrelative: movement between thecommutator cylinder-and: the brushes isaccomplished by moving the entire locomotive 1 backward and forwardalong the track 6 relative to the train 9a suificient distance-to causethe surfacesmay be brought into engagement with the brushes 17 is equalto:

26.75% 10.5 X62 I '132 X 2'6;75; ,52 g It; is, therefore, apparentthatthe heating effect of the starting current may be distributed.throughout the rotor of the driving motor in a manner that simulates-theconditions obtained when-the locomotive is in normal operation along thetrack by simply moving the locomotive backward: and forward ia distanceof/approximately 3% inches. This comparatively small movement: of: thelocomotive is: accomplished; in the preferred inches form-[oftheiinvention, by-m'eans-v of a 'hy- .draulic cylinder 25 that; ismounted on the a friction-draft-gear mechanism 27 of standard designthat is ordinarily securely attached to a. locomotive frame. As'shown inFig. 2, the draft gear 27 and the coupling 8, as utilized in accordancewith the invention, are mountedin a yoke'28 that is disposed to slidelongitudinally relative to the locomotive frame 2 between the guidemembers 29 and 30. The end of the yoke 28 that is farthest from thedrawbar 8 is attached to the piston rod 26 by means of a nut 31. Thepiston rod 26 is provided with a piston 32 that is disposed to be. movedwithin the cylinder 25 by means of fluid pressure that maybe appliedthrough the inlet openings33 and 34.

In Fig. 7 are shown diagrammatically two cylinders v25, one for each endof a 10001110? tive, that are each provided with a piston 32 and apiston rod 26, as shown in'Figs. 2 and 3. In order that fluid pressuremay be applied, pipes 35 and 36 areconnected to the openings 33 and 34',respectively, in each of the cylinders25. These pipes are connected, bymeans of three-way valves 37 and 38 and pipes 39 and 10, to a source offluid pressure, such as a' pump 41. The pump -11 is of the rotaryhydraulic type that is disposed tobe operated continuously in onedirection by means of a driving motor 42 and to supply fluid pressure toeither the pipe 39 or the pipe 40. The flow of fluid is governed, bothas to direction and amount, by the'position of a lever 4E3 that may be 7actuated manually or. by means of a device,

such as an air cylinder 45, that'is provided .with a piston 46 having aspring return mechanism 17. The air cylinder is con.- nected, by meansof a. pipe 48, to a threeway valve 49that is disposed .to connect thepipe 18 to either one of two pipes 51leadmg to reverse valves 52 whichare disposed to cooperate withireversing arms 53-011 each of the pistonrods 26. 7

As shown at the right-hand side of Fig. 7, the valve 52 is utilized toconnect the pipe 51 to a source of fluid pressure, such as the usualcompressed-air lines utilized on, locomotives that may be represented bya pipe 54; The connections between the piston to and thelever 13 aresuch that, when pressure is applied to the piston 46, the lever 43 W-lllbe moved to a position A inopposition to the force exerted by the spring47.

If the train to be started is connected to the right-handend of thelocomotive, that is represented diagrammatically in Fig. 7 by theright-hand cylinder 25 and piston rod 26, the three-way. valves 37,38and 49 are turned, to connect the pipes 39, 40 and 4.8 to the pipes35, 36and 51, respectively, lead+ I opened if the ing to the'oscillatormechanism at the righthand end ofthe locomotive. i I v In order that theoscillator mechanism may functlon as soon as current is applied to thedriving motorv 14, a controlsegment 56, Fig. 12, for controlllngthemotor 42 is incorporated with a locomotive-starting drum 57 that isutilized in a well .known manner for starting" the driving motor 14. Inthe particular structure shown in Fig. 12, the full starting tractive,effort of the locomotive is developed when the controller drum is turnedto position 6, and an overload circuit breaker (not shown) will becontroller ismoved to position f before the train starts. y

The control segment 56 is, therefore, so dimensioned"thalt it will closea circuit 58 extending from a control battery 59 through a contactor 60while thecontrollerfi? is in any one of the first five positions a, 7),a, (Z.

or e; The contactorl 60-is disposed to close a circuit 61 that connects.th-e'moto-r 42 to the battery 59 1n series with a magneticbrakemechanism'62. Consequently, when the starting current is'first applied:to the motor 14 by movingthe controller drum 57 to position a, thecircuit 58is closed by means of the segment 56, thereby energizing thecontactor 60 which closes the circuit '61.

When the circuit 61.v is closed, the magnetic brake 62 is released, andthe motor 42- is energized to drive the pump 41. As long as thecontroller 57 remains on anyone of 3 the first five notches, themotor142will continue to run and operatethe' pump 41 con tinuously in onedirection. o

As hereinbefore explained, the pump 41 will supply fluid pressure. toeither the pipe 39 or the pipe.40 and, starting from the position shownin Fig. 7 pressure willfirst be applied throughvthe pipes '40 and 36 tothe right-hand facesofthe piston 32. he

piston 32 will, consequently, becaused to move slowly to the leftrelative to the cyl inder 25. Inasmuch as the cylinder 'isj rigidlysecured to the locomotive 1, this motion will cause the locomotive to bedrawn towards thetrain-to which: it is attached. When the piston 32approaches the end of its stroke, the reversing arm 53, that is mountedon the piston rod 26 will engage the reversing valve 52 and turn it insuch manner that the p 1pe'.51 Wlll be disconnected from the source .offlu d pressure, represented by the pipe 154, and will be connected tothe atmosphere by means of the passage 55. This will allow the air toescape from the air cylinder andper mit the piston 46 to returnto thehead of the cylinder 45- under the action of the spring 47. 1

The connections between the piston 46 and the lever 43*are suchthatgmovement of thepiston to the head ofthe cylinder 45 causes thelever 43 to move from posit-ionAto position B. When the lever 43 ismoved to position fB,the direction ofthe flow of fluid from the pump 41is changed,

and pressure is applied through the pipes 39 and 35 to the left-handface of the piston 32. Itma-y be further observed that, when the lever43 is in position B, it is at a greater distance from thecenter'position C, than it is when in position A. This is to provide fora greaterflow of fluid to the left-hand side of the piston 32, inasmuchas the piston surface is not thesame oneach side because of the surfaceoccupied by the piston rod 26 on the right-hand side. I fVVhen the lever43 is in position B, the cylinder 25 and the locomotive 1 upon which itis mounted will be caused to move to the left relative to. the piston 32which remainsin substantially constant relation to the train which maybe attached to the locomotive. Of'course, in normal practice, thetractive effort being exerted by the locomo tive will tend to move it tothe left and,

therefore, the pressure in the pipe 36 will pressure in the pipe begreaterathan the Under these conditions, the "pump. 41 will operate as amotor and drive the motor 42 as agenerator. In order that the motor 42may regenerate in this manner, it is desirable that it be operated bycurrent'from the batte1y59, that is normally utilized for auxiliaryapparatus in the. locomotive. 'As shown in Fig. 12, the field 63 of themotor 42 is connected, in shunt to the armature 64, across the terminalsof the battery 59 in such manner that, when it is being driven troller57 is in any of these positions, the

controller segment 56 will be disengaged of whether it is acting as apump from the circuit 58,-thereby deeiiergizing the contactor 60 whichwill, in turn, stop the motor 42 and deenergize the magnetic brake 62.The bralre 62 will then be applied to hold the motor42and the'p'ump 41stationary. hen the pump 41 is held stationary,

sservesessentially as a valve to prevent communlcation betweenthe pipelines 89 and 40,"thereby preventing the passage of fluid from one sideof the pist'on'32 to the other side and serving to hold the piston in asubstantially fixed position. Relief valves 65 are providedlion each ofthe -pipes'39 and-40 and' are connected by means of a pipe a 4- and 66to an overflow reservoir67 in such man.- nor that, it excessive pressureis developed in the pipes 35 and 3.6, it may be reli ved by permittingfluid to escape, through the valves 65 and the pipe .66, to thereservoir 67. I

A further connection 68 is made between the pipe 66 and the pump 41 in.SUCh'IIlELTI- ner that any fluid that may leak through the pump willalso be conducted to the reservoir 67. he relief valves 65furtherfunction in connection with the cylinder and-piston 32 as ahydraulic buffing mechanism. Under normal operating conditions,

, when'the locomotive is pulling a load, the

piston. 32 will be drawn to the end of the cylinder 25 nearest the endof the locomotive, inasmuch as there is always a slight leakage of fluidpast the piston 32 and through the pump 41. It then, the locomotive isuncoupled from the train and is later iecoupled to a train by hackinginto it-in the usual manner, the force of the coupling blow will developexcessive pressure in the pipeline 35 and 39. As hereinbefore explained,the pressure will be relieved through one of the valves 65, therebycushioning the blow and relieving the locomotive frame 2 and other partsfrom excessive. strains. 7

Inasmuch as theliyditaulic system takes the place of a friction-draft.gear to a large extent, the draw-bar mechanism of the 1000- motive maybe constructed as shown inFigs. In these views,.the coupling 8 is showndirectly connected to the piston rod '26by means ofa cross head or guidemember 71 that is disposed to slide between guides 72 that are supportedupon the l0- coinotive frame 2. A pivotal'eonnection 73 isprovidedbetween the draw-bar 8 and the cross head 71 to permit the coupling toswing laterally relative to the locomotive frame. Inasmuch as allrailway cats are provided with friction-draft-gear mechanism, such draftgear is not absolutely necessary on a locomotive for successful.operation and, therefore, a locomotive provided with the hydraulicoscillating mechanism embodying this invention, which, in itself,servesas a butting mechanism, may well dispense with the usualfriction-draft gear.

As shown in Fig. .7, the pipelines 39 and ;are each provided withpressure gauges 7 5 thatmay be utilized to indicate the pressure in thepipe line in the usual manner or may be calibrated-to indicate directlythe draw-bar pull that is being exerted by the locomotive,inasmuch asthe draw-bar pull is obviously in-directproportionto the pressure ineither the pipe line 39'or'the pipe 40.

Toprovide means for returning fluidfrom the reservoir 67. to thehydraulic system, a make-up valve mechanism :76 is connected toeach ofthe pipe lines-39 and'40 andto the .reservoir67l.*lAsi-shown in Fig. 10,the

make-up valve comprises a horizontally dis posed valve chamber 77 havingan inlet opening 78 near its center that-is connected directly tothereservoir 67. .Outletopenings 79 and 80 are provided atthe ends of thechamber 7 7 and are connected to .the pipe lines 39 and 40,respectively. A slidablc valve member. .81 is provided within thechamber 77. When pressure is exerted by the pump 41thr0ugh the pipelinei10, the valve member 81 is forcedto. the position shown in Fig.10,.therebyclosing a'passage- 83 betweenth'e pipe line 40 and thereservoir 67 and opening a passageway 82 between the reservoir 67 andthepipe line39. Inasmuch as suction isexerted upon the pipe line 39 by thepump (11, fluid maybe drawn fromthe reservoir-67 throughthe inletopening78, into the pipe line 39'to make up for an losses that may haveoccurredthrough leakage orthrough the relief valves 65.

\Vhen pressure is being exerted by the pump upon the pipeline 3.9,.itisobvious. that the valve member81 will be moved downwardly, as seen inFig. 10, thereby opening the passageway 8 3 and closing the passageway82 to connect the pipe line40 tothe reservoir (57.

In orderxto utilize'theoscillating mechanism iltfthGlQft-llillld; end ofthe locomotive, as. seen in. Fig. 7, it is simply necessary'for theoperator to turn the valves 37,. 38 and l9to disconnect the cylinder 25and the reversing mechanism 52 at, the right-hand end ofthelocomotivefrointhe pump j llyand its control mechanismv andito connectthe lefthand cylinder 25.aird reversing valve 52 in their stead. v I IIf it is desired to operate a: locomotive wvithin a train, as shown inFig. 9, that is,

tons 32-and the pipelines 39 and. 35. are, con.-

nected'to exert pressure upon the left-hand face of eachof thepistons.:It will,-there- 'toregbe obvious that, when-pressure is applied by thepump 41 tothc pipe line 40, the locomotive 1 will be'moved tothe rightwith respect tothetrain 9 .from position A 'toaposition' 13,115 shown inFig: 9. In a modified .form ofthe' invention, the

oscillation of the draw-bar"mechanism may be accomplished'by mechanicalmeans,such as shown: in Fig. 6. In this -,view.is shown a shaft .91thatinay be connectedyto the draw-bar mechanism in a mannersimila'r tothe connection employed between the piston rod '26. and the coupling. 8.To provide means for moving the-shaft 91relative to of the shaft isprovided with threads 92 that engage internal threads 93 in a nut 94. aThe nut 94 isjournalled inthe frame 2 between guide members 95 andisprovided, on its external surrace, with worm-threads 96 that engage aworm 97 for rotating the nut. In order to prevent the shaft 91' fromturning with the nut 94, a key-way 98 is provided a; the end thereoffor-engaging a key 99 that is secured to thelocomotive frame 2. t isobvious thata motor may be connected to the worm 97 for the purpose ofactuating the mechanical oscillating device, and a standard limit switchreversing mechanism may be applied to theshaft91 for the purpose ofgoverning thedirection of rotation of the motor and thereby controllingthe motion of the draw-bar mechanism.

From the foregoing discussion and description of the apparatus,1t may beseen that the invention provldes means for moving a locomotive relativeto a stationary train to which it maybe attached in such manner that therotors of the driving metors are caused to rock back and forth slow,-

the starting current throughout allof'the commutator bars and the coilsofthe motor.

Although Ihavedescribed specific embodiments of the invention, it willbe obvious to those skilled in theart that various modifications may bemade in the particu-- lar mechanism for moving the locomotive relatlveto the train wlthout departmg from the spirit and scope of the inventionas delined in the appended claims.

I claim as my invention:

1. In an electrical locomotive, in combination, a draw-bar and means forosc-illating the locomotive relative to the draw-bar.

2. In an electrical locomotive, in combination, a driving motor havinga' commutator cylinder and brushes,.a draw-bar, and means for moving thecommutator cylinder relative to the brushes while the draw-bar isstationary relative to the track upon which the locomotive may beoperating.

3. In an electric locomotive, the combination with wheel axles and adriving motor having a commutator cylinder and brushes, of means formoving the locomotive back and forth while the train to which it isattached is at rest and while the motor is en-.

ergized to exert'tractive effort to cause the commutator cylinder tooscillate relative to the brushes, thereby distributing the heatingeffect of the energizing current throughout the commutator cylinder. 7

4. An oscillating system for moving a locomotive relative to the trainto which it is attached that comprises a hydraulic cylin der securelymounted in the locomotive, a piston in the cylinder, a d1awbarmecl1anism secured to the piston, a pump connected tothe cylinder ateach side of the piston, a motor for driving the pump and means forcontrolling the flow of fluid from the pump to' cause the piston tov bemoved back and forth within the cylinder; y l 1 5. Ina railway vehicle,incombinatioma driven Wheel axe, a motor for driving'thewheel axle andmeans other than the driv- 'ing motor for oscillating the vehicle duringthe starting period.

'6. An electric locomotive comprising wheel axles, a frame mounted onthewheel axles, a drivingmotor for propelling the locomotive, a draw-barmechanism for connecting the locomotive to a train and means forosclllatmg the locomotive relative to the tram during the startingperiod to cause'the driving motor to turn slowly, thereby avoid in anyportion'of the ing' heat concentration motor. o

7. Inan electric locomotive, in combination, a draw-bar, hydraulic meansfor moving the locomotive relative to the draw-bar in the longitudinaldirection and control means for automatically reversing the direction ofmotion of the locomotive. ly, thereby distributing'the heating efiect offrame, wheel axles for supporting the frame,

propelling the locomotive, said 7 a motor for motor being provided witha commutator cylinder and brushes, a gear train for con necting themotor to a wheel axle, a drawbar mechanism, and means for moving thelocomotive longitudinally relative to the draw-bar in order that the.commutator cyl 'in'der may be moved relative to the brushes while the.load to which the locomotive is attachedi's' stationary. p

. 10.'An electric locomotive comprisinga frame, wheel axles forsupporting theframe, a motor for propelling the locomotive, said motorbeing provided with a commutator cylinder and brushes, a gear train forconnecting the motor to a wheel axle, aldraw bar mechanism, and means,formoving the locomotive backward and forward a short' distance relativeto the draw-bar at'a substantially constant speed to. cause thecommutator cylinder tooscillate slowly relative to the brushes for thepurpose of distributing the load on the commutator during the for actingiupon the piston to oscillatethe locomotive relative to the draw-bar.

12. In an electrical locomotive, in combination, a draw-bar system forhaulage purposes, a motor provided with a commutator ment o'fthecommutator cylinder and brushes to, distribute the heating of thecommutato-r cylinderduring the application of a tractive eii-or-t by thelocomotive to the draw- "bar system While the drawbar-system isstationary.

14. In an electrical locomotive, in combination, a draw-bar system forhaulage purposes, a motor provided with a commutator cylinder andbrushes disposed to engage the commutator cylinder, and means tor osciljlating the commutator cylinder relative to the brushes during theapplication of a tractive effort by the locomotive to the-drawbar systemWhile the draw-bar system is stationary to distribute the heating of thecommutator cylinder.

15. In an electrical locomotive, in combination, a draw-bar system forhaulage purposes, a motor provided with a commutator cylinder andbrushes disposed to engage the commutator cylinder, and meansindependentcof the motor for oscillating the commutat-or cylinderrelative to thebrushes during thesiapplication of a tractive effortbyt'he locomotive to the draw-bar system While the draw-bar system isstationary to distribute the heating of the commutator cylinder.

} 1,6. In, an electrical locomotive, in combination, a draw-bar systemfor haulage purposes, a motor provided with a commutator cylinder andbrushes disposed to engage the commutator cylinder, and means connectedto the draw-barsystem for effecting relative oscillatory movement of thecommutator cylinder and brushes during the application of a tractiveeilort by the locomotive to the draw-bar system While the draw-barsystem is stationary to distribute the heating of the commutatorcylinder.

17. In an electrical l0comot-ive,in combination, a draw-bar system forhaulage purposes, a motor provided witha commutator cylinder and brushesdisposed to engage the commutator cylinden and means connected to. .thedraw-bar system for effecting relative oscillatory I movement of thecommutator cylinder and brushes independently of the motor during theapplication of a tractive effort by the locomotive to the draw-barsystem While the draw-bar system is stati'onary todistribute theheatingof the commutator cylinder. I

18. In an electrical locomotive, in combi nation, a draw-bar system forattaching the locomotive to a train, a driving motor for actuating thelocomotive and means for moving the locomotivebackward and forwardrelative to the train to which it is attached while the driving motor isexerting tractive eflfort continuously in one direction, whereby themotor is oscillated to distribute heating effects of the startingcurrent.

19. In a railway vehicle, in combination, a draw-bar at each endthereof, .a hydraulic cylinder associated with each draw-bar and meansfor interconnecting the hydraulic cylinders to effect simultaneousiovement of the draw-bars.

20. -A railway vehiclecomprising a frame, hydraulic cylinders carried bythe frame, pistons in the cylinders, draw-bar mechanism connected to thepistons and extending at each end of the vehicle frame and means forinterconnecting the cylinders in such 'manner that movement of onedraw-bar relative to the frame will cause simultaneous movement of theother draw-bar in the same direction.

In testimony whereof, I have hereunto subscribed my name this 12th dayof May,

CHARLES C. VVHITTAKER.

